Metal ions can be eliminated from aqueous solutions using biosorbent, a substance made from plant biomass. This study investigated the potential use of Arundo donax stems as a cheap, natural biosorbent to remove cobalt ions (Co2+) from an aqueous solution. The biosorbent was characterized by the chemical composition analysis (cellulose, hemicellulose, and lignin), the point of zero charge (pHPZC), by scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction analysis, and Fourier-transform infrared spectroscopy. According to the experimental data of kinetic studies, the equilibrium condition of Co2+ adsorption was attained 360 min after the biosorption started. The pseudo-first, pseudo-second, Elovich, and intra-particle diffusion models were used to model the kinetic experimental data. The best compliance was obtained with the pseudo-first order kinetic model, considering the highest value of the coefficient of determination R2 (0.996) and the lowest chi-square (?2) value (0.757). The findings of this study can be applied to the design of batch biosorption systems for the removal of Co2+ ions in real industrial systems.

This work highlights the potential for the synthesis of new PtSnZn catalysts with enhanced efficiency and durability for methanol oxidation reaction (MOR) in low-temperature fuel cells. In this research, PtZn and PtSnZn nanoparticles deposited on high surface area Vulcan XC-72R Carbon support were created by a microwave-assisted polyol method. The electrochemical performances of synthesized catalysts were analyzed by cyclic voltammetry and by the electrooxidation of adsorbed CO and the chronoamperometric method. The physicochemical properties of obtained catalysts were characterized by transmission electron microscopy (TEM), thermogravimetric (TGA) analysis, energy dispersive spectroscopy (EDS) and by X-ray diffraction (XRD). The obtained findings showed the successful synthesis of platinum-based catalysts. It was established that PtSnZn/C and PtZn/C catalysts have high electrocatalytic performance in methanol oxidation reactions. Catalysts stability tests were obtained by chronoamperometry. Stability tests also confirmed decreased poisoning and indicated improved stability and better tolerance to CO-like intermediate species. According to activity and stability measurements, the PtSnZn/C catalyst possesses the best electrochemical properties for the methanol oxidation reaction. The observed great electrocatalytic activity in the methanol oxidation reaction of synthesized catalysts can be attributed to the beneficial effects of microwave synthesis and the well-balanced addition of alloying metals in PtSnZn/C catalysts.

Surface morphology is one of the critical factors affecting the performance of electrocatalysts. Thus, with careful manipulation of the surface structures at the atomic level, the effectiveness of the catalyst can be significantly improved. Heat treatment is an effective method for inducing surface atom rearrangement, hence modifying the catalyst’s characteristics. This study investigated the substrate’s influence and the effect of thermal annealing on the morphology and surface reconstruction of platinum (Pt) thin-film catalysts. Our findings indicate that heat treatment in a reductive atmosphere (95% Ar + 5% H₂) at 300 °C can significantly impact the degree of rearrangement of surface atoms. This process induces long-range ordering, resulting in domains with a high proportion of (111) and (100) sites without an epitaxial template. Considering that the reactivity of low-index platinum single crystals for the methanol oxidation reaction follows the following sequence Pt(111) < Pt(110) < Pt(100), increasing the proportion of (100) planes leads to a notable enhancement (up to three times) in performance, compared to untreated catalysts. Furthermore, considering the amount of precious metal consumed, a mass-specific current density obtained on annealed Pt@Ni is larger by one order of magnitude and ~2 times that obtained on Pt@Cr and Pt@GC_ox catalysts, respectively. Our results demonstrate that an easy-to-implement way of controlling atomic orientations improves catalyst performance. With this contribution, we propose a method for designing improved electrocatalysts, as catalytic reactions occur only at the surface.

This review paper analyses the biosorption of Ni2+ ion by using unmodified bacterial exopolysaccharides (EPS), based on data from available literature, while this system has been investigated less compared to other heavy metals. Nickel is important both as a potential pollutant and as essential microelement in the function of biocatalysts and nickel-enzymes. The focus of the paper is the influence of the chemical composition of EPS, its spatial organization, as well as the role of pH value and the hydration radius of Ni2+ ion in bonding process. The mechanisms of the biosorption for EPS of different composition were analyzed and proposed in relation to the structural and chemical characteristics of the system, and their interpretation is related to the Langmuir and Freundlich isotherm model. The review of the literature shows that bacterial EPS have a significant biosorption potential toward Ni2+ ion and that biosorption of Ni2+ ion with bacterial EPS is the result of several simultaneous mechanisms, where the composition and structure of EPS play a key role.